The United Nations has a very good guide to global issues. You should access this web site and read the sections that are relevant to topics you are going to engage in on your committee.
The UN Global Issues web site is: http://www.un.org/en/globalissues/
Also, the United Nations has many days throughout the year marked as special days to highlight certain priorities or issues. An example is "World Humanitarian Day", marked this year on 19 August. The link to the list of days, and articles about them: http://www.un.org/en/events/observances/days.shtml
The UN Global Issues web site is: http://www.un.org/en/globalissues/
Also, the United Nations has many days throughout the year marked as special days to highlight certain priorities or issues. An example is "World Humanitarian Day", marked this year on 19 August. The link to the list of days, and articles about them: http://www.un.org/en/events/observances/days.shtml
Also for the Special Conference on water: http://www.globalissues.org/article/601/water-and-development
Feel free to download and use these beginner guides to preparing for an MUN conference.